Handle Twilio SMS status callback
Status callback posted by Twilio for outbound SMS/MMS as the message transitions through queued / sent / delivered / failed. Updates the corresponding Message document and broadcasts a socket event so the org sees the latest delivery state.
Body
Twilio-assigned message identifier whose status is being reported.
Delivery state: queued, sent, delivered, failed, undelivered.
Recipient phone number for the outbound message.
Tether-provisioned Twilio number the message was sent from.
Twilio error code when delivery failed (e.g. 30003).
Human-readable error description paired with ErrorCode.
Response
Plain-text acknowledgement (Twilio only checks the 2xx status).
The response is of type string.
"OK"